A redundancy and switching system and method for head and tail positioning equipment of rail train

Abstract

The present invention discloses a redundancy and switching system and method for head and tail positioning equipment of a rail train, comprising a positioning module and an onboard controller arranged at both ends of the train, wherein the onboard controller is provided with ATP and ATO, and the onboard controllers at both ends of the train realize information exchange through an in-vehicle communication network, and the positioning module is provided with a BTM positioning device and a speed measuring device, and the BTM positioning device collects the positioning beacon information beside the track; ATP and ATO complete the train positioning and periodic position update according to the BTM positioning device and the speed measuring device at the local end respectively, and ATP continuously monitors the positioning failure, and when the head end ATP judges that the local end positioning device fails, if it is judged that the tail end positioning device is not failed at this time, the tail end positioning information is switched to update the local end position information. The present invention can avoid the train degradation and emergency braking caused by the loss of positioning, and ensure the operation efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of rail transportation, and in particular relates to a train positioning technology. Background Art

[0002] The existing urban rail train positioning equipment adopts a head-to-tail redundant design, with a set of BTM positioning equipment installed at the head and tail ends of the vehicle. The ATP at the head and tail ends of the vehicle is equipped with an interactive channel, which uses the interactive channel to exchange information, and uses the interactive information to complete the time synchronization and tail end positioning of the head and tail ends. Then, in the event of a fault at the head end, it is determined whether there is a difference between the information at the head and tail ends in the interactive information. If there is no difference or the difference is within the preset threshold, the tail end information can be used in the event of a fault at the head end. If there is a difference in the information at the head and tail ends and the difference is not within the preset threshold, there is a problem at the tail end, and the tail end information cannot be used when a fault occurs at the head end.

[0003] In the prior art, the position of the train is located using the positioning systems at the head end and the tail end respectively, and the error between the positions located by the positioning systems at the head end and the tail end is calculated. When the error is less than a threshold, if the positioning system at the head end fails, the positioning system at the tail end is used to locate the position of the train. Through the positioning redundancy of the head and tail, when the positioning system at one end fails, the position information of the other end is used to ensure that the train can operate normally. However, the current detection method for the failure of the train positioning system cannot switch to the tail end in time before the head end loses its position due to the failure of the positioning system at the head end. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a redundant and switching system and method for the head and tail positioning equipment of a rail train, which can switch to the tail end in time when the tail end positioning system is healthy before the head end positioning system fails and causes the head end to lose its position.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] On the one hand, a method for redundancy and switching of head and tail positioning equipment of a railway train is provided, wherein both the head and tail ends of the train are provided with an on-board controller, a BTM positioning equipment and a speed measuring equipment, the BTM positioning equipment collects the positioning beacon information beside the track, the on-board controller is provided with an ATP and an ATO, the ATP and the ATO calculate the current speed and displacement of the train according to the information collected by the speed measuring equipment, and the method for redundancy and switching of head and tail positioning equipment of a railway train comprises:

[0007] The ATP and ATO in the onboard controllers at both ends complete the train positioning and periodic position update according to the BTM positioning equipment and speed measuring equipment at the local end;

[0008] When the head-end ATP determines that the local positioning device is faulty, if it is determined that the tail-end positioning device is not faulty at this time, it switches to using the tail-end positioning information to update the local position information, and no longer uses the positioning beacon information received by the local end to update the local position.

[0009] Preferably, the method for updating the head-end positioning information when switching to use the tail-end positioning information is as follows:

[0010] When it is determined that the tail-end positioning information matches the local positioning information and the uncertainty of the tail-end positioning information is less than the uncertainty of the local positioning information, or there is no positioning information at the local end, the head-end ATP safe positioning position and the ATO precise positioning position are updated according to the tail-end positioning information combined with the estimated maximum displacement, minimum displacement and precise displacement of the train within the transmission delay time of the head-tail information;

[0011] and / or, when it is determined that the tail-end positioning information does not match the local-end positioning information, the tail-end positioning information is not used to update the local-end positioning position, and the local-end updates the local-end positioning position according to the periodic displacement measured by the speed measuring device;

[0012] And / or, when it is determined that the head-end positioning device has recovered, either continue to use the tail-end positioning information, or directly switch to using the beacon information read by the local positioning device for repositioning.

[0013] Preferably, when ATP determines that any of the following situations occurs, it is determined that the local positioning device fails: the BTM host actively reports the failure for more than a certain period of time; the local ATP determines that a set number of beacons have been missed continuously based on the location information calculated by the local end and the stored electronic map; the local ATP determines that the train location uncertainty calculated by the local end exceeds the maximum allowable positioning uncertainty N%. <N<=100;

[0014] When the local ATP determines that the local positioning device is faulty, it sends an alarm to the peer end. When the head-end ATP determines that the head-end or tail-end positioning device is faulty, it sends an alarm to the TOD.

[0015] When ATP determines that the local positioning device is faulty, it monitors whether the local end has received a set number of beacon messages continuously. If so, it is considered that the local positioning device has recovered.

[0016] Preferably, the BTM positioning devices at the head and tail ends of the train collect beacon information during its travel, and the current train position information and running direction are obtained after the head and tail of the train pass through two consecutive positioning beacons respectively. The train position information includes the maximum head position, the precise head position, and the minimum head position; thereafter, the current position information is periodically updated according to the periodic displacement calculated by the speed measuring device, and the new beacon information is used to reposition when arriving at a new positioning beacon.

[0017] Preferably, the onboard controllers at the head and tail ends of the train realize information exchange between the head and tail ATPs and between the head and tail ATOs through an in-vehicle communication network;

[0018] By calculating the timestamp ulTimeStamp=t0 when the other end sends the information relative to the local time axis, when the local ATP and ATO receive the interactive information from the other end ATP and ATO, the time when the other end sends the interactive information can be obtained, and then the possible maximum displacement, minimum displacement and precise displacement within the delay time of the head and tail information transmission can be calculated.

[0019] Preferably, when ATO and ATP determine that the tail end positioning information should be switched to be used, when it is determined that the tail end has been positioned, a set of position information is calculated according to the following formula, which is recorded as HeadLocFromCc2:

[0020] Maximum head position = the maximum head position in the tail end message + the maximum accumulated displacement of the local end within (the current safety time of the local end – ulTimeStamp + one ATP / ATO cycle);

[0021] The precise vehicle head position = the precise vehicle head position in the tail end message + the precise accumulated displacement of the local end within ((the current safety time of the local end – ulTimeStamp) / 2) time;

[0022] Minimum vehicle head position = the minimum vehicle head position in the tail end message;

[0023] + indicates forward displacement according to the running direction;

[0024] The accumulated displacement is calculated and stored according to the cycle of the speed measuring device at this end;

[0025] If the current head end has been located, first compare whether the vehicle head position range calculated by HeadLocFromCc2 and the vehicle head position range currently located by the local end intersect. If so, calculate the positioning uncertainty of HeadLocFromCc2 and compare it with the uncertainty of the location information currently located by the local end;

[0026] If the positioning uncertainty of HeadLocFromCc2 is smaller, the position information of HeadLocFromCc2 is used as the current train head position information; otherwise, the position information already located at this end continues to be used.

[0027] Preferably, a tail-end precise parking beacon is provided at the entrance of the station, and when the head end switches to use the tail-end positioning information, the tail end reads the tail-end precise parking beacon for repositioning.

[0028] Preferably, three tail-end precise parking beacons are provided, which are respectively 60 meters, 15 meters and 5 meters away from the tail-end antenna position after parking.

[0029] Preferably, after the head-end positioning device recovers, according to a pre-set strategy, when the head-end positioning device recovers, the tail-end positioning information is no longer used to update the local position; or the tail-end positioning information continues to be used until the tail-end positioning device fails, and the tail-end positioning information can no longer be used to update the local position.

[0030] On the other hand, a redundancy and switching system for positioning equipment at the head and tail of a railway train is provided, including a positioning module and an on-board controller arranged at the head and tail ends of the train, the on-board controller is provided with ATP and ATO, and the on-board controllers at the head and tail ends of the train realize information exchange through an in-vehicle communication network, the positioning module is provided with a BTM positioning device and a speed measuring device, and the BTM positioning device collects positioning beacon information on the side of the track; the ATP and ATO respectively complete train positioning and periodic position update according to the BTM positioning device and speed measuring device at this end, the ATP continuously monitors positioning faults, and when the head-end ATP determines that the local positioning device has failed, if it is determined that the tail-end positioning device is not failed at this time, the tail-end positioning information is switched to be used to update the local position information.

[0031] The present invention adopts the above technical solution and has the following beneficial effects:

[0032] 1. It solves the problem of how to switch and use redundant positioning information at the head end. When the positioning uncertainty at the head end is about to reach the maximum allowable positioning uncertainty, it can switch to using the positioning information calculated according to the tail end positioning device, thereby reducing the occurrence of head end positioning failures and improving the availability of on-board ATP and ATO.

[0033] Because a method for detecting train positioning system failures is proposed, it is possible to switch to the tail end in time when the tail end positioning system is healthy, before the head end positioning system fails and causes the head end to lose its position, thereby avoiding train degradation and emergency braking due to loss of positioning and ensuring operational efficiency.

[0034] 2. ATP continuously monitors and locates faults, and can predict, warn and recover faults of positioning equipment at both ends of the train. It can also switch to using positioning information calculated based on information obtained by the rear-end positioning equipment when the front-end positioning equipment fails, thus improving the availability of the system.

[0035] 3. When using the tail-end positioning position to update the head-end position, the train position change caused by the train displacement during the head-to-tail information transmission delay time is taken into account, ensuring the security of the train position envelope calculated by ATP.

[0036] By calculating the possible maximum displacement, minimum displacement and precise displacement within the delay time of the head and tail information transmission, the position change of the train within the delay time of the information transmission between the head and tail can be solved. And by using the speed and displacement measured at the local end within the delay time to calculate, compared with the method of calculating by multiplying the maximum speed and the minimum speed of the train by the delay time, the positioning error caused by the delay time calculation can be reduced.

[0037] 4. By arranging corresponding precise parking beacons outside the station, it is possible to achieve precise parking by manual or ATO entry even after the head-end positioning device fails and switches to the positioning information calculated based on the information obtained by the tail-end positioning device.

[0038] The specific technical solutions adopted by the present invention and the beneficial effects brought about by them will be disclosed in detail in the following specific embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0040] Figure 1 It is a schematic diagram of the vehicle system composition;

[0041] Figure 2 It is a schematic diagram of the principle of estimating the timestamp of the time when the other party sends the message relative to the time axis of the local machine;

[0042] Figure 3 It is a schematic diagram of the beacon layout of the platform when entering the station from one side and the addition of tail-end precise parking beacons outside the station. DETAILED DESCRIPTION

[0043] The technical solutions of the embodiments of the present invention are explained and described below in conjunction with the drawings of the embodiments of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work are all within the protection scope of the present invention.

[0044] There are onboard systems at both the front and rear ends of the train. Figure 1 As shown, each vehicle-mounted system includes a safety computer (i.e., vehicle-mounted controller), safety platform software, ATP, ATO, and TOD. The safety computers at both ends and the safety computers and the local TOD are connected using the in-vehicle communication network. The in-vehicle communication network interface is a dual-network redundant Ethernet interface to ensure redundant data transmission between the in-vehicle CC cabinets at both ends.

[0045] In addition, the vehicle-mounted system is connected to the vehicle-ground communication unit. A beacon information reading module BTM (i.e., BTM positioning device) and a speed measuring device are installed at each end of the vehicle. The BTM positioning device collects the positioning beacon information beside the track, and the speed measuring device measures the speed. The cab-activated end is determined as the head end, and the non-cab-activated end is determined as the tail end.

[0046] The head and tail ends respectively collect positioning beacon information through BTM positioning equipment during the train's travel. After the BTM antennas at the head and tail pass through two consecutive positioning beacons, ATO and ATP obtain the beacon information and calculate the train's running direction based on the front and rear position relationship of the two positioning beacons read successively in the stored electronic map. Then, based on the position of the second beacon read in the electronic map, the most likely accurate position of the BTM antenna when the BTM antenna receives the second beacon can be obtained. Taking into account the beacon installation error and the beacon reading error, the maximum possible BTM antenna position and the minimum possible BTM antenna position when the BTM antenna receives the second beacon can be obtained. Considering the transmission time from the BTM antenna receiving the beacon information to ATP and AT The maximum possible displacement, minimum possible displacement, and precise displacement of the train within the time when the beacon information is obtained. ATP and ATO can calculate the maximum BTM antenna position, minimum BTM antenna position, and precise BTM antenna position when ATP and ATO obtain the beacon information based on the maximum possible BTM antenna position, minimum possible BTM antenna position, and most possible precise BTM antenna position. Then, based on the minimum possible length, maximum possible length, and most possible precise length of the BTM antenna from the current locomotive coupler, and the offset direction of the running direction, the minimum BTM antenna position, maximum BTM antenna position, and precise BTM antenna position are added respectively, thereby calculating the maximum locomotive position, minimum locomotive position, and precise locomotive position of the current locomotive. Afterwards, the current position information is updated periodically (ATP cycle is 150 milliseconds, ATO cycle is 50 milliseconds) based on the periodic displacement calculated by the speed measuring device, and the new beacon information is used to reposition when a new positioning beacon is read, thereby reducing positioning uncertainty.

[0047] After ATP obtains the current position information, it continuously monitors the uncertainty of the current position information. The uncertainty of the current position information is the distance between the maximum head position and the minimum head position. If the uncertainty of the current position is greater than the preset maximum allowable uncertainty threshold, the current position information is discarded and the position information is obtained again by passing through two consecutive positioning beacons.

[0048] After ATP obtains the current position information, it monitors the number of beacons that have been missed continuously based on the current maximum antenna position and minimum antenna position information and the electronic map information stored in ATP. If the minimum antenna has passed a beacon but has not received information about the beacon before, it is determined to be a missed beacon.

[0049] ATP continuously monitors the positioning fault, and can determine whether there is a fault in the positioning device and give an alarm. ATP continuously monitors whether it receives the faults actively reported by the BTM host. When ATP judges any of the following situations, it judges that the local positioning device has a fault: when ATP judges that it continuously receives the faults actively reported by the BTM host for more than a pre-set time, such as 5s; continuously misses reading a pre-set number of beacons, such as 8; the uncertainty of the current position has exceeded N% (0 < N <= 100) of the pre-set maximum allowable uncertainty threshold (for example: 80 meters), such as: 95%.

[0050] When ATP judges that the local positioning device has a fault or the tail-end positioning device has a fault, it sends an alarm message to TOD, and TOD displays the alarm message. Therefore, it can realize the pre-judgment, alarm and recovery judgment of the positioning device faults at both ends of the train.

[0051] Information is mutually sent between the ATPs at both ends of the train head and tail and between the ATOs at both ends through the in-vehicle communication network. The main information sent between the ATPs at both ends is: whether the local end has been positioned, the maximum calculated head position of the local end, the accurate head position, the minimum head position, the status of the local positioning device (fault / non-fault). The main information sent between the ATOs at both ends is: whether the local end has been positioned, the maximum calculated head position of the local end, the accurate head position, the minimum head position.

[0052] When the head-end ATP judges that the local positioning device has a fault, if it judges that the tail-end positioning device has no fault at this time, it should switch to use the tail-end positioning information to update the local position information, and do not use the positioning beacon information received by the local end to update the local position.

[0053] Among them, the method for updating the head-end positioning information when switching to use the tail-end positioning information is as follows:

[0054] When it is judged that the tail-end positioning information matches the local positioning information and the uncertainty of the tail-end positioning information is less than the uncertainty of the local positioning information, or when there is no local positioning information, the head-end ATP safe positioning position and the ATO accurate positioning position can be updated according to the tail-end positioning information combined with the possible maximum displacement, minimum displacement and accurate displacement of the train within the estimated head-tail information transmission delay time (see the calculation description of the maximum cumulative displacement and accurate cumulative displacement in the following formula, and the minimum displacement is considered to be 0).

[0055] When it is judged that the tail-end positioning information does not match the local positioning information, the tail-end positioning information cannot be used to update the local positioning position, and the local end updates the local positioning position according to the periodic displacement measured by the speed measurement device.

[0056] When it is determined that the head-end positioning device has recovered, the tail-end positioning information can continue to be used, or the beacon information read by the local positioning device can be directly switched to reposition.

[0057] Therefore, the problem of how to switch and how to use redundant positioning information at the head end is solved. When the head-end positioning uncertainty is about to reach the maximum allowable positioning uncertainty, it is possible to switch to using the positioning information calculated according to the tail-end positioning device, thereby reducing the occurrence of head-end positioning failures and improving the availability of on-board ATP and ATO.

[0058] The security platform computers at both ends maintain a millisecond-level local current security time from the start. When the local security platform computer receives information from the other end, it calculates a timestamp ulTimeStamp=t0 when the other end sends this message relative to the local computer, such as Figure 2 shown.

[0059] When the head-end ATP determines that the local positioning device is faulty and the opposite-end positioning device is not faulty, it determines that the positioning information obtained from the tail-end positioning device should be switched to use, and sends the tail-end positioning information to be used to the ATO.

[0060] When ATO and ATP determine that the tail end positioning information should be switched to use, and when it is determined that the tail end has been positioned, a set of position information is calculated according to the following formula, recorded as HeadLocFromCc2:

[0061] Maximum head position = the maximum head position in the tail end message + the maximum accumulated displacement of the local end within (the current safety time of the local end – ulTimeStamp + one ATP / ATO cycle);

[0062] The precise vehicle head position = the precise vehicle head position in the tail end message + the precise accumulated displacement of the local end within ((the current safety time of the local end – ulTimeStamp) / 2) time;

[0063] Minimum vehicle head position = the minimum vehicle head position in the tail end message;

[0064] Note: + means forward offset according to the running direction;

[0065] The calculation method of the maximum / precise cumulative displacement within a period of time is as follows: First, ATP and ATO periodically calculate the maximum periodic displacement, precise periodic displacement, maximum periodic speed, and precise periodic speed within each period based on the data provided by the speed measuring device at this end, and store them, and record the time period corresponding to the periodic displacement and periodic speed. When it is necessary to calculate the maximum (or precise) cumulative displacement within a period of time, it is necessary to find all periodic time periods included in the period of time, and add up the periodic maximum (or precise) displacement within all periodic time periods. If there is less than one periodic time period, the corresponding displacement is calculated by multiplying the periodic maximum (or precise) speed of the period by the time, so that the maximum (or precise) cumulative displacement within a period of time can be calculated. Among them, the calculation of the maximum periodic displacement, precise periodic displacement, maximum periodic speed, and precise periodic speed of each period is explained below using the OPG installed on the wheel axle as the speed measuring device as an example. The main principle of using OPG for speed and distance measurement is that when the wheel rotates, the vehicle transmission plate drives the OPG tongue to rotate, and the OPG converts the number of wheel rotations into the number of pulses. ATO and ATP periodically calculate the travel distance and speed based on the change in the number of pulses. Specifically, ATP and ATO collect the accumulated pulse count value and pulse frequency in each cycle. The displacement of the train in each cycle is calculated by multiplying the number of changes in the pulse count in each cycle by the pulse distance (the train travel distance corresponding to one OPG pulse), and the speed of the train in each cycle is calculated by multiplying the pulse frequency by the pulse distance. The pulse distance is calculated based on the wheel diameter where the OPG is located and the number of pulses generated by the OPG when the wheel rolls one circle, that is, pulse distance = wheel diameter * π / the number of pulses generated by the OPG when the wheel rolls one circle. Due to the error in the wheel diameter, the maximum pulse distance, precise pulse distance and minimum pulse distance can be calculated based on the maximum wheel diameter, precise wheel diameter and minimum wheel diameter respectively. According to different pulse distances and cycle speed and cycle displacement calculation methods, the maximum cycle speed, precise cycle speed, minimum cycle speed, maximum cycle displacement, precise cycle displacement and minimum cycle displacement can be calculated respectively.

[0066] If the current head end has been positioned, first compare whether the vehicle head position range calculated by HeadLocFromCc2 overlaps with the vehicle head position range currently positioned by this end. If so, calculate the positioning uncertainty of HeadLocFromCc2 and compare it with the uncertainty of the current position information already positioned by this end.

[0067] If the positioning uncertainty of HeadLocFromCc2 is smaller, the position information of HeadLocFromCc2 is used as the current train head position information; otherwise, the position information already located at this end continues to be used.

[0068] If the current head end is not located, HeadLocFromCc2 is directly used as the current train head position information.

[0069] Therefore, by calculating the possible maximum displacement, minimum displacement and precise displacement within the delay time of the head and tail information transmission, the position change of the train within the delay time of the information transmission between the head and the tail can be solved. And by using the speed and displacement measured at the local end during the delay time to calculate, compared with the method of calculating by multiplying the maximum speed and the minimum speed of the train by the delay time, the positioning error caused by the delay time calculation can be reduced.

[0070] After ATP determines that the local positioning device has failed, it continues to monitor whether it has received information about multiple beacons with continuous positions in the map. If the number of beacon information with continuous positions received reaches a preset threshold, such as 3, it is determined that the local positioning device has recovered.

[0071] After the head-end positioning device recovers, you can choose to stop using the tail-end positioning information to update the local position according to the pre-set strategy. Or you can continue to use the tail-end positioning information and use the beacon information obtained by the local end from the positioning device for repositioning until the tail-end positioning device fails, and then you can no longer use the tail-end positioning information to update the local position.

[0072] Furthermore, a tail-end accurate parking beacon is added at the station entrance. Figure 3 As shown, there are three tail-end precise parking beacons, which are about 60 meters, 15 meters, and 5 meters away from the tail-end antenna position after parking. When the head end switches to use the tail-end positioning information, the tail end can read the added tail-end precise parking beacon for repositioning to reduce the positioning error, and then the head end updates the local position according to the updated position of the tail end. As the speed is getting lower and lower during parking, the displacement within the transmission delay time is getting closer and closer to 0, so that the head end can achieve precise parking after entering the station, improving the availability of the system.

[0073] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for redundancy and switching of head and tail positioning equipment of a rail train, wherein both the head and tail ends of the train are provided with an on-board controller, a BTM positioning equipment and a speed measuring equipment, wherein the BTM positioning equipment collects the positioning beacon information beside the track, and the on-board controller is provided with an ATP and an ATO, wherein the ATP and the ATO calculate the current speed and displacement of the train according to the information collected by the speed measuring equipment, wherein: The rail train head and tail positioning equipment redundancy and switching method includes: The ATP and ATO in the onboard controllers at both ends complete the train positioning and periodic position update according to the BTM positioning equipment and speed measuring equipment at the local end; When the head-end ATP determines that the local positioning device is faulty, if it is determined that the tail-end positioning device is not faulty at this time, it switches to using the tail-end positioning information to update the local position information, and no longer uses the positioning beacon information received by the local end to update the local position; During the running of the train, the BTM positioning devices at both ends collect beacon information. After the front and rear ends of the train pass through two consecutive positioning beacons, the current train position information and running direction are obtained. The train position information includes the maximum front position, the precise front position, and the minimum front position. After that, the current position information is updated periodically according to the periodic displacement calculated by the speed measuring device. When a new positioning beacon is reached, the new beacon information is used to reposition. The on-board controllers at the front and rear ends of the train realize information interaction between the front and rear ATPs and between the front and rear ATOs through the in-vehicle communication network. By calculating the timestamp ulTimeStamp = t0 when the opposite end sends the information relative to the local time axis, when the local ATP and ATO receive the interactive information of the opposite end ATP and ATO, the time when the opposite end sends the interactive information is obtained, and then the possible maximum displacement, minimum displacement and precise displacement within the transmission delay time of the front and rear information are calculated. When ATO and ATP determine that the tail end positioning information should be switched to use, and when it is determined that the tail end has been positioned, a set of position information is calculated according to the following formula, recorded as HeadLocFromCc2: Maximum head position = maximum head position in the tail end message + maximum accumulated displacement of this end within (current safety time of this end – ulTimeStamp + one ATP / ATO cycle); The precise vehicle head position = the precise vehicle head position in the tail end message + the precise accumulated displacement of the local end within the time ((the current safety time of the local end – ulTimeStamp) / 2); Minimum vehicle head position = the minimum vehicle head position in the tail end message; + means forward offset according to the running direction; The accumulated displacement is calculated and stored according to the cycle of the speed measuring device at this end; If the current head end has been located, first compare whether the vehicle head position range calculated by HeadLocFromCc2 and the vehicle head position range currently located by the local end intersect. If so, calculate the positioning uncertainty of HeadLocFromCc2 and compare it with the uncertainty of the location information currently located by the local end; If the positioning uncertainty of HeadLocFromCc2 is smaller, the position information of HeadLocFromCc2 is used as the current train head position information; otherwise, the position information already located at this end continues to be used.

2. The method for redundancy and switching of head and tail positioning equipment of a railway train according to claim 1, characterized in that: The method for updating the head-end positioning information when switching to use the tail-end positioning information is as follows: When it is determined that the tail-end positioning information matches the local positioning information and the uncertainty of the tail-end positioning information is less than the uncertainty of the local positioning information, or there is no positioning information at the local end, the head-end ATP safe positioning position and the ATO precise positioning position are updated according to the tail-end positioning information combined with the estimated maximum displacement, minimum displacement and precise displacement of the train within the transmission delay time of the head-tail information; and / or, when it is determined that the tail-end positioning information does not match the local-end positioning information, the tail-end positioning information is not used to update the local-end positioning position, and the local-end updates the local-end positioning position according to the periodic displacement measured by the speed measuring device; And / or, when it is determined that the head-end positioning device has recovered, either continue to use the tail-end positioning information, or directly switch to using the beacon information read by the local positioning device for repositioning.

3. The method for redundancy and switching of head and tail positioning equipment of a railway train according to claim 1, characterized in that: When ATP determines that any of the following situations occurs, it is considered that the local positioning device is faulty: the BTM host actively reports the fault for more than a certain period of time; the local ATP determines that a set number of beacons have been missed continuously based on the location information calculated by the local end and the stored electronic map; the local ATP determines that the train position uncertainty calculated by the local end exceeds the maximum allowable positioning uncertainty of N%. <N<=100; When the local ATP determines that the local positioning device is faulty, it sends an alarm to the peer end. When the head-end ATP determines that the head-end or tail-end positioning device is faulty, it sends an alarm to the TOD. When ATP determines that the local positioning device is faulty, it monitors whether the local end has received a set number of beacon messages continuously. If so, it is considered that the local positioning device has recovered.

4. The method for redundancy and switching of head and tail positioning equipment of a railway train according to claim 2, characterized in that: A tail-end precise parking beacon is set at the entrance of the station. When the head end switches to use the tail-end positioning information, the tail end reads the tail-end precise parking beacon for repositioning.

5. The method for redundancy and switching of head and tail positioning equipment of a railway train according to claim 4, characterized in that: There are three tail-end precise parking beacons, which are 60 meters, 15 meters and 5 meters away from the tail-end antenna position after parking.

6. The method for redundancy and switching of head and tail positioning equipment of a railway train according to claim 1, characterized in that: After the head-end positioning device recovers, according to the pre-set strategy, when the head-end positioning device recovers, the tail-end positioning information will no longer be used to update the local position; or the tail-end positioning information will continue to be used until the tail-end positioning device fails, and the tail-end positioning information can no longer be used to update the local position.

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